Enantioselective cyclization of bromoenynes: mechanistic understanding of gold(I)-catalyzed alkoxycyclizations

Identifier:  imarina:9499047

Handle: https://hdl.handle.net/20.500.11797/imarina9499047

Authors:  Cataffo, Andrea; Garcia-Padilla, Eduardo; Escofet, Imma; Fincias, Nicolas; Arnanz, Anna; Zuccarello, Giuseppe; Tian, Guilong; Cai, Luyu; Khorasanidarehdor, Fereshteh; Maseras, Feliu; Echavarren, Antonio M

Abstract:
The first enantioselective gold(I)-catalyzed alkoxycyclization of bromo-1,6-enynes has been achieved using a modified JohnPhos ligand bearing a distal C-2-chiral 2,5-diarylpyrrolidine unit. Using an achiral catalyst of the same family, the enantioselective cascade cyclization of bromo-1,5-enynes to form polycyclic scaffolds was also accomplished for the first time. Interestingly, performing the cyclization of bromo-1,6-enynes in the absence of an alcohol nucleophile led to the formation of nearly racemic cycloisomerization products. Control experiments and DFT calculations support a mechanism involving an in-cycle racemization process mediated by a 1,2-hydrogen shift, shedding new light on the mechanism of gold(I)-catalyzed alkoxycyclizations.